This invention relates to a fuel injection system for use with a multi-cylinder internal combustion engine.
In diesel engines in general, the rotational speed of the engine tends to become unstable in a low load and low speed region such as an idling region, making it difficult to maintain stable engine operation. This is because in such operating region of the engine, fuel is supplied to the engine in such small quantities that the fuel injection quantity can fluctuate to a large degree, resulting in degraded atomization of the injected fuel.
Further, a diesel engine is generally apt to produce large combustion noise and an increased amount of NOx while it is operating in a low load and low speed region in the vicinity of an idling region, because this type engine depends upon self-ignition of fuel injected into the cylinders, which gives rise to a time lag between the fuel injection and the self-ignition of injected fuel. This time lag can be long particularly in the low load and low speed operating region of the engine wherein degraded fuel atomization impedes smooth vaporization of the injected fuel. As a reuslt, combustion of the injected fuel can take place at one time, causing large combustion noise and increased combustion temperature.